Dislocations and extended defects in AlN deformed at high temperatures

Polycrystalline AIN could be deformed up to 10% strain in compression at elevated temperatures (1820-1920 K) under constant stress in the range 150-250 MPa or at a fixed strain rate of 5.6 x 10(-6) s(-1). Stress-strain curves show a marked temperature dependence. TEM investigations point to cavitation at grain boundaries as the main source of damage. Intragranular plasticity is achieved mainly by (a) over right arrow-type dislocations. A few dislocations with (c) over right arrow + (a) over right arrow Burgers vectors could also be observed. (C) 1997 Elsevier Science S.A.